How to add an item to an existing customer order?

Is there a way to manually add an item from your catalog to an existing customer order (invoice)?

For example, I have a customer who purchased a "blue widget". He completed the checkout process and paid for the item. After sending the payment he called to add a "red widget" to the existing order. He wants to add to the existing order so he can take advantage of the combined shipping price (versus paying the full shipping charge on two seperate orders).

I cannot figure out how to manually add an item to an existing order (invoice). IS this even possible?

Any help would be appreciated.

Install the Super Orders module and you will be able to do this and much more.

Thanks for the information styledata! I'll try the Super Orders module as you suggested.

Sorry for the delayed response.